Patent Literature 1: JP-A-1987-042225
Conventionally, a measurement apparatus measuring a distance is known. The measurement apparatus emits a search wave, measures a flight time of the search wave corresponding to a time from when the search wave is emitted to when a reflected wave is received, and measures the distance from the measurement apparatus to a front object. The search wave is a light pulse, which is a light signal having a pulse form, for example.
A mass spectroscope measures a flight time of a particle and calculates a mass spectrum of a sample (referring to patent literature 1). A signal of an observation object is sampled and stored in a memory in the mass spectroscope. In order to save a memory space, the signal in a predetermined time domain is sampled selectively and is stored in the memory.
The applicants of the present disclosure have found the following with respect to a measurement apparatus.
According to the measurement apparatus measuring the distance to the front object referring to the flight time, a distance measurement with high precision may be required to sample a receiving signal of a reflected wave with a high sampling frequency. However, when all receiving signals are sampled with the high sampling frequency, a memory space for a data accumulation may be increased.
In a technology field of a vehicle mounted apparatus, a receiving signal of a reflected wave may be sampled with a low sampling frequency, and the receiving signal of the reflected wave from a front object of a short distance having a short flight time may be selectively sampled with a high sampling frequency.
According to this manner, the distance of a distant front object may be immeasurable with high precision. In addition, in an measurement apparatus measuring a distance to an object positioned at a vehicle front, since a moving object such as a person, a vehicle or the like exists freely, it may be difficult to measure the distance to the front object with high precision irrespective of a distance in contrast to the mass spectroscope in which the time domain of a sampled object is set to a fixed domain.